[Effect of parathyroidectomy on enamel formation of incisors in rats]

A chronological study on the enamel formation of the incisors in male Wistar rats was undertaken following parathyroidectomy by using glyoxalbis (2-hydroxyanil) stain, ground sections, and scanning and transmission electron micrographs. In addition, the effect of activated vitamin D3 administration on the enamel formation in parathyroidectomized rats was investigated using the same procedures. The following results were obtained. 1) Effects of parathyroidectomy (1) Macroscopic observation and the changes in body weight. The tetany after parathyroidectomy was not observed in this study. However, the reduction of behavior, loss of glistening of body hair, and standing of body hair became evident with time. There was a tendency for loss of the increased body weight as compared with that in normal rats. In the incisors, there were no macroscopic abnormal findings in shape and color. (2) Chronological alterations in serum Ca and P concentration. Serum Ca concentration decreased abruptly until 1 week after parathyroidectomy and the condition of lower concentration of serum Ca remained unchanged after 2 weeks of parathyroidectomy. Serum P concentration increased until 2 weeks after parathyroidectomy, but thereafter it decreased slightly and additionally the condition of higher concentration of serum P remained unchanged. (3) Morphological alterations in ameloblast layer and enamel matrix. No evident changes were observed at the stage of division and proliferation of ameloblasts after parathyroidectomy. But in the morphology of ameloblasts and intercellular organelle at the stage of formation and maturation, various changes were observed: namely atropy, deformities and degeneration of ameloblasts, irregular swelling, disruption and liberation of rough endoplasmic reticulum, disappearance of attached ribosomes, indistinctness of Golgi apparatus, expansion of perinuclear space, reduction in number of mitochondria and loss of crista. In the ameloblasts at the stage of matrix formation and maturation, vacuoles of various sizes were observed, and increases in number and growth in size were seen chronologically. Furthermore, after 4 weeks of parathyroidectomy, cyst formation was observed and enamel hypoplasia was limited only to the superficial layer of enamel. Calcium value at the site of enamel tubules was one fiftieth as much as that of normal rats on the ameloblastic side after 5 weeks of parathyroidectomy and was reduced to one-half at intermediate site. Similarly, P value was reduced.(ABSTRACT TRUNCATED AT 400 WORDS)